1. Field of the Invention
The present invention relates to a manufacturing method of functional film and a functional film, and particularly, to a manufacturing method of functional film, on which an organic film and an inorganic film are deposited on a substrate, and a functional film.
2. Description of the Related Art
Various functional films, such as gas barrier films, protective films, optical filters, anti-reflective films, and other optical films, are used in various apparatuses, such as optical elements, display devices such as liquid crystal displays and organic EL displays, semiconductor devices, and thin-film solar cells.
Deposition techniques based on vacuum deposition methods, such as sputtering and plasma CVD, are used to manufacture the functional films. A so-called roll-to-roll technique for continuous deposition on a lengthy substrate is implemented to efficiently manufacture the functional films with high productivity. Japanese Patent Application Laid-Open No. 8-92727 discloses an example of a manufacturing method of functional film (for example, barrier film), in which acrylate monomer, etc., is applied to a substrate that is continuously driven, the film is taken up into a roll after drying and curing, the roll including an organic film is fed to a vacuum deposition apparatus, and an inorganic film is deposited on the organic film.
Japanese Patent Application Laid-Open No. 2009-86022 discloses heating at least one of protective films at a predetermined temperature range in a polarizing plate including the protective films on both sides of a polarizing film. As a result, a polarizing plate with excellent dimensional stability can be obtained for a long time. The protective films of Japanese Patent Application Laid-Open No. 2009-86022 is used to protect a completed product (polarizing plate).
Japanese Patent Application Laid-Open No. 8-92727 discloses a method of setting a film roll of roll hardness 70 to 95 on a feeding unit of a vacuum deposition apparatus and continuously depositing inorganic films on a substrate to uniform the quality of the functional films by preventing a roll gap in the deposition of inorganic films.
However, even if the film roll including the organic films is taken up at the roll hardness 70 to 95, the film roll takes in entrained air when the substrate is taken up. If the film roll with the entrained air is set to the feeding unit of the vacuum deposition apparatus with reduced pressure, the entrained air in the film roll comes out.
As a result, the balance of stress (tension and friction) inside the film roll during take-up is lost, and the film roll makes a motion of “tight winding (roll diameter shrinkage)”.
When the “tight winding” occurs, the organic film on the substrate may be rubbed against the back side of the substrate on the upper side or may touch the dust attached on the back side of the substrate in the film roll. Therefore, minute explosions of film occur in the organic film, and the smoothness is lost. If the substrate is transferred and the inorganic film is deposited on the organic film, a deposition failure occurs, and there is a problem of cracks or holes in the inorganic film.
Furthermore, the performance of the functional film is affected if the organic film or the inorganic film touches the guide roller when the guide roller transfers the substrate including the organic film or the inorganic film deposited in the vacuum deposition apparatus. Since there is no entrained air in the vacuum deposition apparatus as opposed to the atmosphere, the contact, i.e. friction, with the guide roller is large. Minute film destructions occur if the organic film touches the guide roller before the deposition of the inorganic film. If the inorganic film touches the guide roller after the deposition of the inorganic film, minute scratches occur because the inorganic film is significantly thin, and there is a problem that the barrier performance is lost.
If the used substrate is thin and soft, deflections and vertical wrinkles easily occur in a width direction depending on the tension necessary for the transfer. As a result, force is applied to a location where the guide roller and the substrate locally contact, and the organic films and the inorganic films are easily broken. Furthermore, if a fold occurs in the substrate, there is a problem that a crack easily occurs in the organic film and the inorganic film.
To solve the problems, there can be a method of supporting only the edges of the substrate and transferring the substrate without touching the deposition surface. The vertical wrinkles of the substrate increase due to the tension if the substrate is thin. Therefore, the productivity needs to be significantly reduced by very slowly transferring the substrate or by enlarging the area of the supported part.
Meanwhile, in view of the productivity, cost, and use applications, the reduction in the thickness is strongly demanded in relation to the type and thickness of the substrate. In the deposition method of the inorganic film, such as a barrier film, there is also a step of exposing the substrate to a heat source. Therefore, the substrate needs to be cooled from the opposite side (back side) of the deposition side. A cooling drum and the substrate are adhered to cool the substrate, and it is important to control the tension of the substrate during transfer.
A problem of the thin functional film, such as a barrier film, using the roll-to-roll technique is that the functional layer of the functional film needs to be protected during a deposition/transfer process, during a storage/transport process, and during an assembly process.
As for the characteristics of laminate films to be used, vertical wrinkles or folds of the substrate during transfer, take-up to the film roll, prevention of scratches on the inorganic films, etc., need to be taken into consideration when a plurality of organic films and inorganic films are laminated on the substrate to form the functional layer. Protection of the functional layer also needs to be taken into consideration when the completed functional film is laminated on another product.